The present specification is directed to a monitor for detecting failures in the installation of neon gas light transformers comprised of an electronic circuit installed within the transformer compartment in order to control and turn off the transformer in the event any failure may occur. A neon gas sign of the invention has one or more neon tubes.
As is known, a number of failures may occur in a transformer used for the purpose of supplying power to neon gas signs, and the inventive monitor was realized to detect such failures in order to overcome them. Three main types of failures can occur in a transformer. The monitor of the invention is able to detect these individually or in any combination, sequentially or not. The first type of failure is when an interruption of the secondary current is caused by any broken neon gas tube or interruption along the high-voltage cables. The second type of failure that may occur is when there is a current leakage from the secondary coil to the ground wire that is caused by a high-voltage leakage, when the insulation of the high-voltage cable connected between the transformer and the neon gas sign is not suitable. The third type of failure is when the transformer case is not correctly connected to the ground wire of the installation, due to a broken ground wire or even an incorrect installation.
Currently when the above mentioned failures occur in the installation of neon gas sign transformers, the transformer remains activated, thus supplying unnecessary power, and this is dangerous in view of the fact that it has a high-voltage outlet that can reach up to 15,000 Volts, remaining in this condition until the failure is overcome. Therefore, the worldwide market requires more safety in this particular. See the standard imposed by the United States called USA-UL2161; that sets out measures for preventing neon gas sign transformers from remaining active when the above mentioned failures occur.
In order to satisfy this market demand, the present applicant has developed a monitor for detecting failures in the installation of neon gas sign transformers based on a programmed digital micro-controller that is connected to the transformer. For this disclosure a neon gas sign is a sign with one or more neon tubes. The secondary coils are connected to the transformer. The secondary coils are connected to the ground wire through optical couplers and the output signal of the optical couplers provide the micro-controller with the current xe2x80x9cstatusxe2x80x9d of the condition of the transformer secondary. The micro-controller provides a xe2x80x9cTRIACxe2x80x9d with an exciting current that turns on/off the primary of the transformer under the AC voltage of the distribution network and also supplies a current to turn on a red LED when there is a failure and a green LED that indicates if any failure has occurred.
When the neon gas sign operates regularly, the TRIAC is activated and the transformer remains activated and the red LED remains inactivated while the green LED remains activated. When there is any failure in the installation, the monitor detects the failure immediately, and the transformer is immediately turned off and six seconds later it is automatically turned on again. If the cause of the failure has disappeared, the transformer continues operating normally. However, if the failure persists, the transformer is switched off for a second time, and six seconds after the transformer is switched on again. If the failure still persists, the transformer is definitively switched off for a third time, at which time a warning LED starts blinking also showing the type of failure that took place until a maintenance expert comes to the site and makes the required repair.
The purpose of the warning LED is to guide the maintenance expert by showing the type of failure that took place, in the following way: one blink per second to indicate that the load of the secondary is interrupted, meaning that there is a broken neon tube or gas sign or wire; two blinks per second to indicate current leakage escape through the cables of the transformer secondary and; three blinks per second to indicate the lack of connection with the ground wire of the installation. Thus, the maintenance expert will be able to repair the failure in a quick and quite sure way, because any time the warning LED blinks under any of the above mentioned conditions the transformer will be switched off. On the other hand, after repairing the failure, the expert must wait at least one minute before connecting the transformer to the distribution network again, because if the power is supplied to the transformer before one minute has elapsed, the protection circuit continues storing the failures that took place previously and it will not allow the transformer to start operating again. Only after said one minute period has elapsed with the transformer switched off all the failures stored in the protection circuit are overcome and the transformer can be switched on again with zero failure.
The monitor for detecting failures is also provided with a deactivating button that makes it possible to intentionally connect it to the transformer for a time not longer than twenty minutes. This intentional connection can only be used when failures are caused by a broken neon gas sign, or tube or tubes or a current leakage through the cables or wires of the transformer secondary. For safety reasons, the deactivating button cannot be activated when the failure is due to lack of connection with the ground wire of the installation. This button is provided to make it easier to find the failure for the sake of maintenance of the neon gas sign.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.